U.S. Pat. No. Re. 30,408, reissued Sept. 30, 1981, to the assignee of the present application, discloses railway brake appratus including a brake cylinder device and a control valve device. The usual air reservoirs associated with conventional pneumatic brake equipment are eliminated in the disclosed apparatus in favor of storing the compressed air within the brake cylinder device itself. The brake cylinder device embodies a pair of tandem-connected pistons of unequal diameter, the larger piston cooperating with the brake cylinder body to form on the respective opposite sides of this piston two chambers that are charged with compressed air via the train brake pipe, and in which chambers the air required for use by the brake apparatus, including the brake cylinder device, is stored. The aforementioned control valve device operates in response to variations in the train brake pipe pressure to control the transfer of air stored in the brake cylinder device, so as to develop differential forces across the respective pistons thereof, and thereby effect a brake application and brake release.
In addition to the typical packing cup type pressure seals associated with the respective pistons of this brake cylinder device, there are several additional areas in which dynamic sealing is required, all of which are critical in the sense that leakage thereat affects the desired operation of the brake cylinder device.
Further, passageways are required in the body of the brake cylinder device to conduct pressure between the control valve device and brake cylinder operating components. It is well known that the expense in the manufacture of a casting increases with the complexity in the configuration of these passages, as well as in the shape of the casting itself.